Are you a pay monthly or pay as you go (Big Bundle) customer @RP3 ?
Do you have an Android or iPhone?
Have you got WiFi calling enabled on your account/phone?
Depending on the answers the help would change.
I'll leave the community guide about voicemail here in case that helps.
Guide: All you need to know about O2 Voicemail 901
Please note, this is not customer services and we cannot access your account. Do not publish personal details (email, phone number, bank account).
Link to our guide on how to contact them can be found here
